The Liberal Democrats insist that allegations of sexual misconduct by a former party chief will not affect their chances in the Eastleigh by-election on Thursday, despite indications that the race may be getting tighter.

Nick Clegg will make his fourth visit to the Hampshire constituency today as questions grow about the party’s handling of claims of impropriety against women by Lord Rennard, the Lib Dems’ election strategist.

Senior Lib Dem politicians are understood to be nervous about the impact of the scandal on their vote, but a spokesman in Eastleigh said they had seen few indications that it was a